Special Conditions: Learjet Inc., Model LJ-200-1A10 Airplane; Crashworthiness, Emergency Landing Conditions, 7372-7373 [2014-02611]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 79, Number 26 (Friday, February 7, 2014)]
[Rules and Regulations]
[Pages 7372-7373]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-02611]



[[Page 7372]]

-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2013-0857; Special Conditions No. 25-528-SC]


Special Conditions: Learjet Inc., Model LJ-200-1A10 Airplane; 
Crashworthiness, Emergency Landing Conditions

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

-----------------------------------------------------------------------

SUMMARY: These special conditions are issued for the Learjet Inc. Model 
LJ-200-1A10 airplane. This airplane will have a novel or unusual design 
feature when compared to the state of technology envisioned in the 
airworthiness standards for transport category airplanes. This feature 
is a hybrid construction that uses both composite and metallic 
materials in the structure for which the crashworthiness responses for 
occupant safety may not be equivalent to current all-metallic 
airplanes. The applicable airworthiness regulations do not contain 
adequate or appropriate safety standards for this design feature. These 
special conditions contain the additional safety standards that the 
Administrator considers necessary to establish a level of safety 
equivalent to that established by the existing airworthiness standards.

DATES: Effective Date: March 10, 2014.

FOR FURTHER INFORMATION CONTACT: Mark Freisthler, FAA, Airframe and 
Cabin Safety Branch, ANM-115, Transport Airplane Directorate, Aircraft 
Certification Service, 1601 Lind Avenue SW., Renton, Washington, 98057-
3356; telephone 425-227-1119; facsimile 425-227-1320.

SUPPLEMENTARY INFORMATION:

Background

    On February 9, 2009, Learjet Inc. applied for a type certificate 
for their new Model LJ-200-1A10 airplane (hereafter referred to as the 
``Model LJ-200''). The Model LJ-200 is a business class airplane 
powered by two high-bypass turbine engines with an estimated maximum 
takeoff weight of 35,550 pounds and an interior configuration for up to 
10 passengers.
    The current design includes a skin-stringer fuselage configuration. 
The pressure fuselage will consist of monolithic carbon fiber 
reinforced plastic (CFRP) skin, with CFRP and metallic frames above 
floor level, and CFRP longerons and stringers. All substructure will be 
mechanically fastened to the skin. Fasteners for stringers aligned 
along the length of the co-cured splice will provide fail-safe 
capability for the splice. Cabin entry door frames, over-wing exit door 
frames, and frames below floor level will be metallic. Attachment of 
pressure bulkheads, windshield frame, and splicing concepts will be 
adjusted for any skin thickness variation that occurs. The wing 
consists of resin transfer infusion skins with composite spars and 
metallic ribs. The empennage consists of composite sandwich skins with 
metallic spars and ribs. The airframe has a sandwich construction for 
the nose and empennage structures.
    There are no existing regulations that adequately address the 
potential difference between metallic fabricated airplanes and 
composite fabricated airplanes with regards to impact response 
characteristics for what are considered survivable crash conditions. 
The CFRP fuselage constitutes a novel and unusual design feature for a 
transport category airplane. These special conditions are necessary to 
ensure a level of safety equivalent to that provided by Title 14, Code 
of Federal Regulations (14 CFR) part 25.

Type Certification Basis

    Under the provisions of 14 CFR 21.17, Learjet Inc. must show that 
the Model LJ-200 meets the applicable provisions of part 25, as amended 
by Amendment 25-1 through 25-127 thereto.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the Model LJ-200 because of a novel or 
unusual design feature, special conditions are prescribed under the 
provisions of Sec.  21.16.
    Special conditions are initially applicable to the model for which 
they are issued. Should the type certificate for that model be amended 
later to include any other model that incorporates the same novel or 
unusual design feature, the special conditions would also apply to the 
other model under Sec.  21.101.
    In addition to the applicable airworthiness regulations and special 
conditions, the Model LJ-200 must comply with the fuel vent and exhaust 
emission requirements of 14 CFR part 34 and the noise certification 
requirements of 14 CFR part 36; and the FAA must issue a finding of 
regulatory adequacy under Sec.  611 of Public Law 92-574, the ``Noise 
Control Act of 1972.''
    The FAA issues special conditions, as defined in 14 CFR 11.19, in 
accordance with Sec.  11.38, and they become part of the type 
certification basis under Sec.  21.17(a)(2).

Novel or Unusual Design Features

    The Model LJ-200 will incorporate the following novel or unusual 
design feature: Hybrid construction using both composite and metallic 
materials in the structure for which the crashworthiness responses for 
occupant safety may not be equivalent to that of all-metallic 
structure.

Discussion

    The Model LJ-200 fuselage is fabricated using CFRP skins with 
aluminum ribs and stringers. This hybrid construction may behave 
differently from similar, fully-metallic structure due to differences 
in material ductility, stiffness, failure modes, and energy absorption 
characteristics. Therefore, the impact response characteristics of the 
Model LJ-200 must be evaluated to ensure the survivable crashworthiness 
characteristics are not significantly different than those of a 
similarly-sized airplane fabricated from traditionally-used metallic 
materials.
    The FAA and industry have been working together for many years to 
understand how transport airplane occupant safety can be improved for 
what are considered survivable accidents. This work has involved 
examining airplane accidents, conducting tests to simulate crash 
conditions, and developing analytical modeling of a range of crash 
conditions, all with the purpose of providing further insight into the 
factors that can influence occupant safety. Results of this on-going 
effort have enabled specific changes to regulatory standards and design 
practices to improve occupant safety. This evolution is reflected in 
changes to the part 25 emergency landing condition regulations. For 
example, airplane emergency load factors in Sec.  25.561, General, have 
been increased, and passenger seat dynamic load conditions have been 
added (Sec.  25.562, Emergency landing dynamic conditions).
    The seat dynamic load conditions were added to the regulations 
based on FAA and industry tests and a review of accidents. They reflect 
horizontal and vertical accelerations/time environment generated by 
previously certificated airplane designs given conditions that were 
survivable. These tests also demonstrated that the performance of the 
airframe was acceptable in a dynamic impact event. In the evolution of 
the regulations, there is at present no specific dynamic regulatory 
requirement for airplane-level crashworthiness.

[[Page 7373]]

However, the FAA requires an assessment of each new model airplane to 
ensure that the airplane will not significantly depart from typical 
dynamic characteristics found in previously certificated designs.
    The nature of the assessment is largely dependent on the 
similarities and differences between the new type design and previously 
certificated airplanes. Such an assessment ensures that the level of 
safety of the new composite designs corresponds to the level of safety 
achieved with similar metallic designs around which the existing 
regulations were written. If significant trends in industry warrant 
change to the existing regulations, the FAA and industry rulemaking 
process may be used to develop an appropriate dynamic regulatory 
requirement for airplane level crashworthiness.
    The FAA and industry have collected a significant amount of 
experimental data as well as data from crashes of transport category 
airplanes that demonstrated a high occupant survival rate at vertical 
descent velocities up to 30 ft/sec (on a single aisle airplane). Based 
on this information, the FAA finds it appropriate and necessary for an 
assessment of the Model LJ-200 to span a range of airplane vertical 
descent velocities (up to 30 ft/sec, or that appropriate for a 
comparable size airplane).
    The FAA expects the Model LJ-200 to exhibit similar crashworthiness 
capabilities under foreseeable survivable impact events as achieved by 
previously certificated transport category airplanes of similar size 
and configuration. In order to make this assessment, criteria need to 
be established by which the similarities and differences between new 
type designs and previously certificated airplanes may be analytically 
evaluated. Based on the FAA's evaluation of the intent of existing 
regulations, the following areas need to be evaluated to demonstrate 
comparable behavior of the Model LJ-200 design to currently 
certificated transport category airplanes:
     Retention of items of mass. It must be shown that the 
occupants, i.e., passengers, flight attendants, and flight crew, will 
be protected during the impact event from release of seats, overhead 
bins, and other items of mass due to the impact loads and resultant 
structural deformation of the supporting airframe and floor structures.
     Maintenance of occupant emergency egress paths. The 
airframe must not deform such that rapid evacuation of occupants is 
impeded.
     Maintenance of acceptable acceleration and loads 
experienced by the occupants.
     Maintenance of a survivable volume. All areas of the 
airplane occupied for takeoff and landing must be shown to provide a 
survivable volume during and after the impact event.

Discussion of Comments

    Notice of proposed special conditions No. 25-13-08-SC for the 
Learjet Inc. Model LJ-200 airplanes was published in the Federal 
Register on October 31, 2013 (78 FR 65235). No comments were received, 
and the special conditions are adopted as proposed.

Applicability

    As discussed above, these special conditions are applicable to the 
Learjet Inc. Model LJ-200-1A10. Should Learjet Inc. apply at a later 
date for a change to the type certificate to include another model on 
the same type certificate incorporating the same novel or unusual 
design feature, the special conditions would apply to that model as 
well.

Conclusion

    This action affects only certain novel or unusual design features 
on one model of airplanes. It is not a rule of general applicability.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type certification basis for Learjet Inc. Model LJ-200-1A10 
airplanes.

Crashworthiness, Emergency Landing Conditions

    In order to demonstrate an equivalent level of occupant safety and 
survivability to that provided by previously certificated transport 
category airplanes of similar size and configuration under foreseeable 
survivable impact events, Learjet Inc. must demonstrate that the Model 
LJ-200-1A10 meets the following criteria for a range of airplane 
vertical descent velocities up to 30 ft/sec:
    1. Retention of items of mass. The occupants, i.e., passengers, 
flight attendants, and flightcrew, must be protected during the impact 
event from release of seats, overhead bins, and other items of mass due 
to the impact loads and resultant structural deformation of the 
supporting airframe and floor structures. The applicant must show that 
loads due to the impact event and resultant structural deformation of 
the supporting airframe and floor structure at the interface of the 
airplane structure to seats, overhead bins, and other items of mass are 
comparable to those of previously certificated transport category 
airplanes of similar size for the range of descent velocities stated 
above. The attachments of these items need not be designed for static 
emergency landing loads in excess of those defined in Sec.  25.561 if 
impact response characteristics of the Model LJ-200-1A10 yield load 
factors at the attach points comparable with those expected for a 
previously certificated transport category airplane of similar size.
    2. Maintenance of acceptable acceleration and loads experienced by 
the occupants. The applicant must show that the vertical acceleration 
levels experienced at the seat/floor interface and loads experienced by 
the occupants during the impact event are consistent with those found 
in Sec.  25.562(b) or with the levels expected for a previously 
certificated comparable transport category airplane of similar size.
    3. Maintenance of a survivable volume. The applicant must show that 
all areas of the airplane occupied for takeoff and landing provide a 
survivable volume comparable to that of previously certificated 
transport category airplanes of similar size during and after the 
impact event. This means that structural deformation will not result in 
infringement of the occupants' normal living space significantly 
affecting their survivability or egress.
    4. Maintenance of occupant emergency egress paths. The applicant 
must show that the airframe deformation after the vertical impact event 
does not impede the rapid evacuation of occupants comparable to 
previously certified transport category airplanes of similar size.

    Issued in Renton, Washington, on January 31, 2014.
John P. Piccola, Jr.,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2014-02611 Filed 2-6-14; 8:45 am]
BILLING CODE 4910-13-P